|Year : 2023 | Volume
| Issue : 5 | Page : 20-23
Oral hibernoma along with multiple lipomas
Mahaboob Shahnaz1, Nair Shalini1, Abdul Qayyum Shereefa1, Kuruvilla Vikas2
1 Department of Oral Pathology, PSM College of Dental Sciences and Research, Akkikavu, Kerala, India
2 Department of Oral Surgery, PSM College of Dental Sciences and Research, Akkikavu, Kerala, India
|Date of Submission||14-Jun-2022|
|Date of Decision||22-Jun-2022|
|Date of Acceptance||27-Jun-2022|
|Date of Web Publication||04-Feb-2023|
Department of Oral Pathology, PSM College of Dental Sciences and Research, Akkikavu – 680 519, Kerala
Source of Support: None, Conflict of Interest: None
| Abstract|| |
'Hibernoma' is a neoplasm that arises from vestiges of fetal brown fat, and its occurrence in oral cavity is extremely rare. Its most common locations include thighs, the inter-scapular region, and the cervical region. In the present case, a 37-year-old male patient reported to our department with a localized swelling on his lower left labial mucosa along with multiple cutaneous well-defined swellings on his right arm and abdominal region. Incisional biopsy was carried out. Histopathological examination revealed sheets of multi-vacuolated eosinophilic cells with the granular cytoplasm interspersed with fat cells suggestive of oral hibernoma. These are rare lesions and could be often a missed-out diagnosis. Therefore, it is imperative to consider oral hibernoma among the commonly considered differential diagnosis of oral mucosal swellings.
Keywords: Brown fat, lipoma, oral hibernoma, rare benign tumour, S100 positivity
|How to cite this article:|
Shahnaz M, Shalini N, Shereefa AQ, Vikas K. Oral hibernoma along with multiple lipomas. J Oral Maxillofac Pathol 2023;27, Suppl S1:20-3
|How to cite this URL:|
Shahnaz M, Shalini N, Shereefa AQ, Vikas K. Oral hibernoma along with multiple lipomas. J Oral Maxillofac Pathol [serial online] 2023 [cited 2023 Mar 22];27, Suppl S1:20-3. Available from: https://www.jomfp.in/text.asp?2023/27/5/20/369173
| Introduction|| |
Hibernomas are rare benign soft tissue tumours arising from brown fat tissues. The term hibernoma was given by Grey in 1914. These tumours are usually slow-growing and mostly asymptomatic unless they cause compression of neighbouring structures that may lead to secondary symptoms. It is commonly seen in the age group between the third and fifth decades.
It is an extremely rare lesion to occur in the oral cavity such that the previous literature has reported very few cases on sites such as the tongue and labial mucosa., From a macroscopic perspective, it is well-defined, soft, and mobile, and the colour varies from tan to red brown, depending on the amount of intra-cellular lipid.
They were initially thought to resemble vestigial fat-storage organ cells analogous to those of hibernating animals, in which this tissue is believed to have a thermoregulatory function. The brown adipose tissue is rich in glycogen, cholesterol, and phospholipids and enables energy from oxidized lipids to dissipate as heat. Lipoma is the most common type of soft tissue tumour. Multiple lipomas localised in different areas of the body are rare and can occur in specific hereditary syndromes.
| Case Report|| |
A 37-year-old healthy male patient reported to our department with a localised swelling on his lower left labial mucosa measuring roughly around 0.8 × 0.5 × 0.7 cms [Figure 1]. Along with this, there were a few other multiple sub-cutaneous well-defined swellings on his right arm and lower abdominal region which were previously diagnosed as lipomas [Figure 2]. The family history and drug history were non-contributory to the swelling. The swelling was fluctuant and exhibited a positive slip sign. After thorough evaluation of his oral swelling, initially, a provisional diagnosis of oral mucocele was made, following which its excision was carried out under local anaesthesia [Figure 3].
|Figure 1: Clinical image showing well-defined localised swelling in the left lower labial mucosa having the same colour as that of the adjacent normal mucosa|
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|Figure 2: Clinical image showing multiple well-defined swellings on the right upper arm region|
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|Figure 3: Clinical image showing excisional biopsy that was carried out under local anaesthesia.|
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The gross pathology of the lesion showed a well-defined band of yellow matter along the course of the specimen in addition to other creamish and brownish areas [Figure 4]. Histopathological examination of the lesion revealed sheets of multi-vacuolated eosinophilic cells with a granular cytoplasm and eccentric nuclei interspersed with uni-vacuolated mature fat cells suggestive of oral hibernoma [Figure 5], which can be appreciated in hand illustration [Figure 6]. A negative periodic acid Schiff staining along with his previously diagnosed cutaneous lipomatosis contributed to the confirmatory diagnosis of the same. An immuno-histochemistry test was also performed using an S100 marker, which turned out to be positive again, suggestive of hibernoma [Figure 7].
|Figure 4: Grossing image showing a well-defined band of yellow matter along the course of the specimen in addition to other creamish and brownish areas|
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|Figure 5: Histopathological image showing sheets of multi-vacuolated eosinophilic cells with a granular cytoplasm and eccentric nuclei interspersed with uni-vacuolated mature fat (H&E stain; 40X magnification)|
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|Figure 6: Hand illustration depicting hibernoma. (A) Mature fat cells. (B) Hibernoma cells with a granular eosinophilic cytoplasm. (C) Connective tissue septa|
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|Figure 7: Immuno-histochemical staining of lesional cells with S100 (IHC; 10Xmagnification)|
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| Discussion|| |
Hibernoma is a rare benign tumour composed of brown fat. It was first described in humans in 1906 by Merkel and named by Grey in 1914. Brown fat occurs normally in the human foetus, being distributed in the neck, axillae, and sub-pleural regions. It may also be present in neonates but will gradually decrease, beginning at about 8 weeks. The location of many hibernomas corresponds to the foetal distribution. These tumours have been reported to occur most commonly in the inter-scapular area, neck, axilla, and mediastinum, although the thigh was found to be the most common site in a recent review.
The peak incidence reported in the literature is the third decade of life. The mean age of diagnosis is usually 38 years. It is seen as the highest in the typical variant and the lowest for the myxoid type.
Slight male predilection is favoured especially for typical and lipoma-like hibernoma variants.
The pathogenesis of hibernomas is unclear. Although they appear to develop from residual deposits of brown fat, these tumours have also been observed in locations where brown fat is usually absent. Of interest is the report of an intra-cranial hibernoma that presented mimicking a meningioma and another case of scalp hibernoma.
Hibernoma in the parapharyngeal space is an exceedingly rare entity. Hibernomas in this location clinically present as a non-painful bulge in the lateral pharyngeal wall and often come to light incidentally.
Radiographs are limited in the evaluation of non-mineralized lesions such as hibernomas. Among them, sonography is most effective in evaluating hibernomas of the sub-cutaneous soft tissues. Sonographic findings suggest that these neoplasms are generally encapsulated and well circumscribed with similar echogenicity to surrounding fat. On T1 imaging in magnetic resonance imaging (MRI), they are typically heterogeneous in signal and can be slightly hypo-intense or iso-intense to surrounding subcutaneous fat. T2 signal is also increased because of increased vascularity compared to white fat.
The histopathological picture consists of a variable percentage of brown fat cells which are eosinophilic and polygonal, and they usually demonstrate a granular and multi-vacuolated cytoplasm. These usually contain a variable component of uni-vacuolated fat cells. The stroma may be consisting of spindled cells or myxoid components. They have a high concentration of cytochrome pigments.
Hibernomas differ in the content of their multi-vacuolate adipocytes and uni-vacuolate adipocytes. Furthermore, they vary in the appearance of the polygonal brown fat cells and also associated small capillary proliferations.
Four morphologic variants of hibernoma have been identified: typical, myxoid, spindle cell, and lipoma-like. “Typical” hibernoma, the most common (82.4%), includes eosinophilic cell, pale cell, and mixed cell types based on the tinctorial quality of the hibernoma cells. The myxoid variant (8.2%) contains a loose basophilic matrix. Spindle cell hibernoma (2.4%) presents features of spindle cell lipoma and hibernoma, all occurring in the neck or scalp. The lipoma-like variant (7%) contains only scattered hibernoma cells.
In a study performed by Furlong M.A et al. in 2001, immuno-histochemical studies for S-100 were performed on 20 selected cases, representing most morphologic variants. Among them, most hibernomas, 17 of 20 (85%), showed positivity for S-100, ranging from focal to diffuse. Multi-vacuolated hibernoma cells more often demonstrated stronger positivity than the uni-vacuolated white fat cells.
The differential diagnosis of hibernomas includes lipoma, adult rhabdomyoma, chondroid lipoma, liposarcoma, granular cell tumour, and meta-static renal cell carcinoma. The usual treatment consists of surgical excision, and the prognosis is excellent. Local recurrence does not generally occur. Intra-lesional or incomplete excision may however result in continued growth and local recurrence.
| Conclusion|| |
Hibernomas are in general rare lipomatous lesions, and to our knowledge, only two previous cases of oral hibernoma, one on the tongue and one on the lower labial mucosa, have been reported. It could be often because of a missed-out diagnosis, and hence, it is imperative that in addition to the commonly considered differential diagnosis of oral mucosal swellings such as mucocele and haemangioma, even oral hibernomas are considered from henceforth.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]